I saw this on another forum and thought I'd share it here for those that might be interested.
I know it costs major £££ when it comes to upping the power on an n/a but still, very interesting to see what needs to be done in order to get more from this particular engine.www.roadandtrack.net.au/images/stories/d...non-turbo_engine.pdf

I reckon a skimmed head, 2.2 stroker running racing fuel with timing advance and inlet and exhaust cams with standalone engine management would see significant results. Would not be for the faint hearted though.